1. Field of the Invention
The present invention relates generally to semiconductor manufacturing and, more particularly, to a method for etching a face of an object and an object thereby etched.
2. Background
In the packaging process of semiconductor devices, after semiconductor devices are formed on a front face of a silicon substrate, they are divided into individual units.
The packaging process generally includes a substrate lapping step for reducing the thickness of a silicon substrate, a sawing step for sawing the silicon substrate to divide it into individual chips, a die attaching step for bonding the individual chips so that they attach to die pads of lead frames, a wire bonding step for electrically connecting the chip to leads of the lead frames, a molding step for molding the chips using molding plastics, a soldering step for plating exposed leads of the lead frames, and a folding and cutting step for shaping the soldered leads into desired shapes.
The substrate lapping process is performed to adjust the thickness of the substrate in accordance with a design specification of a semiconductor package, without damaging the front face of the substrate where the semiconductor devices are formed. The substrate-lapping step generally includes a grinding step and a polishing step. The above substrate lapping process has the advantage of being rapidly performed at a cost that is relatively low.
Generally, in the substrate lapping process that includes the grinding and polishing steps, a protective tape is attached to the front face of the substrate where the semiconductor devices are positioned in order to prevent the front face of the substrate from being damaged. The grinding step roughly grinds a rear face of the substrate, while the subsequent polishing step is used to precisely polish the rear face of the substrate. The grinding step differs from the polishing step in the processing parameters of each step, such as polishing pads used, sorts of slurries needed, rotation speeds of the rotating plates, and so on. After completing the polishing step, the protective tape is removed from the front face of the substrate.
When the substrate lapping process is attempted on a substrate having a thickness of less than about 150 μm, cracks are frequently generated in the substrate. Additionally, the slurries are often introduced between the protection tape and the front face of the substrate during these steps. Thus, the semiconductor devices on the front face of the substrate may be damaged during the lapping process. A method is therefore needed to etch the rear face of a substrate to a desired thickness while minimizing the damage to the substrate and preventing failures of the semiconductor devices on a front face of the substrate.